Audio oscillator



June 7, 1938.v s. sNEAD 2,119,971

vpro oscILLATQR origina; Filed oct. 5, 1954 TIME- 0 mzoaoaosowmmfnn DIAL SETTING Cillin. 00

AUDIQ OSCILLATOR Sam Snead, Milwaukee,

Wis., assigner to The Otoiiex Corporation, Milwaukee, Wis., a corporation ci Wiscenn Application October 5, 1934, Serial No. 746,988 Renewed November d, 1937 14 elaine.

This invention relates to audio oscillators for the production of audio waves having a distinctive Wave form which greatly departs from the sinusoidal wave which is desired in oscillators used heretofore.

.I have found that audio sounds having certain wave forms and controllable i'n frequency and volume are particularly useful for the treatment and alleviation of certain defects of the ear and to provide an oscillator capable of producing such soundwaves is an object of the present invention. v

It has also been found that when stimulating hearing by a continuous sound of constant intensity and pitch, the hearing mechanism becomes gradually accustomed thereto and does not respond any longer. If, on the other hand, the pitch of the sound is varied continuously Within limits of audibility, the hearing is continuously stimulated. It has further been found that hear-v ing mechanism, when impaired, frequently does not respond to a single sound stimulation. However, if such stimulation isv repeated for several separated intervals in succession, the summation d of such stimuli results in a response resulting in perception of the sound. To provide a method of and apparatus for automatically producing such variation and repeated stimuli is another object of my invention.

The aforedescribed stimulation is further improved by varying the pitch from one limit to the 'other in steps whereby'the variation is temporarily reversed but so that the net result is a variation in the desired direction. Such variation is known as pilgrim steps wherein ripples are superimposed upon the main oscillatory variation, and to provide a method of and appa ratus for such automatic variation in pilgrim" 'steps is another object of my invention.

Another object is to provide an electrical oscillator producing audio waves havingl harmonics of relatively' high amplitude.

Another object is to provide an oscillator of the aforementioned type which is easily adjustable for varying frequencies Within the audible range.

Another object is to provide an oscillator, the volunie of which is adjustable over a Wide range without affecting the frequency for which it is adjusted.

Another object is to provide an oscillator having constant wave shape for varying frequency and Volume.

Another object is to provide an oscillator in which the sound frequency is automatically The accompanying drawing is'illustrative of one embodiment of my invention. In the drawing.

Figure 1 is a connection diagram of an oscillator built in accordance with my invention.

Fig. 2 is an oscillogram of the wave shape of the output of the oscillator.

Fig. 3 is a curve showing the relation between the setting of the dial for controlling the frequency and the frequency of the output.

Fig. 4 is a similar diagram showing the relation between the setting of the frequency adjusting dial and the volume of the output.

Fig. 5 is a diagram showing the variations of the sound frequency with time for one cycle of such variations, while Fig. 6 is a drawing illustrating the mechanism` for automatically varying the sound frequency;

Referring to Fig. 1. theoscillator consists of a high vacuum tube i, having a heater la for heating the cathode ib, an` anode i, a control grid Id and a screen grid le. The heater i as well as the heaters of the other tubes to be described subsequently may be supplied with heating energy in a Well known manner from any suitable source.

A second tube 2 similar in all respects to the tube i has a heater 2a, a cathode 2b, an ariode 2c, a control grid 2d and a screen grid 2e. Connected in cascade with the tubes i and 2 in a manner to be described hereafter is a modulator tube 3 having-a heater 3W, a cathode 3b,an anode 3c, a control grid "3d, a screen `grid 3e and a second screen grid 31. The output of the tube 3 is amplied in the tube fi having-a. cathode-heater 4, a cathode db, an anode 4 and a control grid 4i, and the outputof the tube lil is further amplied by a tube 5 having a heater 5a, a cathode 5b, an 50 anode 5, a control grid 5d and a screen grid 5e. An output transformer 6 having a primary winding 6 and a secondary winding 6b connects the tube 5 to aseries of telephone jacks by which the energy controlled by said tube 5 is to be received. 55

The apparatus also includes an inductance 1 one end terminal of which is connected to the negative grounded terminal of a source of power supply, while the other end terminal is connected through a condenser 8 and a parallel resistor 9 to the grid Id. An intermediate terminal of the inductance 1 is connected to the cathode Ib.

A second inductance I0 similar to the inductance 1 has its one end terminal' connected to the negative terminal of the power supplyaforementioned, while its other end terminal is connected to the grid 2d in series with a condenser II which is in-parallel with a resistor I2. Connected in parallel with the inductance` 1, between the grid Id and the negative terminal are a xed condenser I3 of suitable capacity and a smaller adjustable condenser I4, the purpose of which will be explained hereinafter. A fixed condenser I5 and a smaller adjustable condenser I3 are .con-

nected in parallel with the inductance I0. An

'impedance I1 has one terminal connected to the anode I while its other terminal is connected to one terminal of a resistor I8, the other end of -thelatter being connected to the anode 2. A

condenser I9 is connected between the anode I and the control grid 3d and a similar condenser 20 ls connected in series with the resistor 2l between the anode 2 and the .control grid 3d. The common terminal of the condenser 20 and the resistor 2| is connected through a resistor 22 to the negative line.

by a resistor 22. An impedance 231 has one terminal connected to the anode 3-and isparalleled by two similar condensers 24 and 25 which are connected in series' and their common terminal is connected to the negative line. The other terminal of the impedance is connected to the high voltage positive supply terminal through resistance 23. The common terminal of impedance23 and resistance 26 is connected through a condenser 21 to one fixedv terminalfof a poteny which is connected to the negative terminal ofA tiometer resistor 28, the other fixed terminal of the power supply, while the sliding contact of said potentiometer is connected to the control grid 4. The cathode 4b is connected to the negative terminal of the power supply through a resistor 29 paralleledby a condenser 33.

The anode 4 is connected to the high voltage positive terminal through resistor 3I and is also connected through a condenser 32 to the grid 5d. The latter is connected to the negative terminal of the power supplythrough resistances 33 and 34 which are in series with each other, the resistance 34 being paralleled bya by pass condenser 35. A resistor 33 connects the cathode 5b to the negative line and is paralleled by a by pass condenser 31. The screen grid 5 lsconnected to the high voltage positive terminal of the power supply while the screen grids I, 2 and 3 are connected to an' intermediate voltage positive ter- Vminal of the power supply.

A condenser 22 connects the cathode 3b with the negative line and is paralleled type telephone receiver which may be employed in connection with the oscillator so that the total load on the transformer 6 is not varied if a receiver is plugged into the jack and'thus substituted in the circuit for the impedance 39'or 4 I. `Referring to Fig. 6, the movable plates of condenser IG are mounted on a rotatable shaft 53' carrying a pulley 5I. Astring or wire 52 is wrapped around the pulley so that it rotates ther eccentrically on a wheel 51 which in turn is rotatably mounted on a sleeve -54 and the latter rotates about a pivot 58. A suitable motor or other driving means 60- carries on its shaft a gear 6I which meshes with the gear "51.* A gear 52 is keyed to the aforesaid sleeve and engages gear 56. A second gear identical to gear 82 isl keyed to the aforesaid sleeve and meshes with a gear 63 fastened to the motor shaft.

As the motor is rotated the connecting rod 53 is recprocated forth and back and thus oscillates the shaft 50 of the condenser I5 with each revolution of the gear 51. [Simultaneously -the motion imparted to the rod I53 by the rotation of gear 51 is modified by "pilgrim steps by virtue of the rotation of pin 55 around the center of pinion* 55.

The wire 52` and pulley 5I may obviously be replaced by a rack and pinion drive, or a lever,

fastened to the shaft 50and hinged to the rod-53, l

may be substituted. Other modifications of such connection are obvious; The number of pilgrim steps .per cycle may be varied by varying thev gear ratios of the transmission, while the length of the pilgrim steps may be varied by varying the eccentricity of the pin 55.

In the operation of thedevlce, the oscillating -circuit which includes tube I and condensers I3 and I4 is adjusted for a frequency of, forex In other words, during that half of the cycle when vthe grid has a relatively low voltage the tube operates on the lower bend of said characteristic, while during the other half cycle the tube operates on the steep; substantially straight portion. As a result the plate current' is practically zero during the greater portion of'the half cycle when the tube operates on the lower bend. Furthermore, the impedance I1 which receives the output current of the tube I is made of relatively low value with respect to the tube impedance lin order to increase in a well known manner the ratio of the effective currents passed by the tube during said respective half cycles, that is, to increase the amj plitude distortions. 'I'he present arrangement, due to the non-resonant operation also produces distortions between the input and output of the tube, which results in a different ampliflcationf of the various frequency components or frequency distortion of the output voltages and currents relative to the input voltages and currents.

The oscillator tube 2 is caused to oscillate in a manner similar to the tube I by adjustment of the condenser I6 but the frequenc'y of oscillation of tube 2 is soadjusted that it heterodynes with tube I so that the difference frequency is within the audible range and this audio frequency may be varied by adjusting the condenser I 6.

The constants of the impedance I8 and the bias of the grid 2d are chosen in a manner similar to that aforedescribed in connection with tube I-.

The combined output of the two oscillators I and 2 is impressed upon the tube 3 which is resistance coupled with the generating tubes I and 2. The output energy of the tube 3 is impressed' upon the tube 4, the radio frequency ripples being filtered out in a well known manner by the impedance 23 and the condensers 2li and 25, while the audio frequency wave is not distorted from its original shape. The tube is again resistance coupled to the tube 3. The ratio between the input of the tube 6 and the output of the tube 3 can'be controlled by adjustment of the potentiometer 28 in a well known manner.

The output of the tube 4 is further amplified by the tube 5 which is coupled with the former by a resistance coupling in a well known manner, while the connection of the transformer S to the tube 5 also presents nothing novel. By arranging the jacks and resistors controlled thereby in the manner aforedescribed, the load on the tube 5 is always kept constant irrespective of the number ofA receivers plugged in so that no variable load reacts upon the device and thereby causes reactions von the frequency of the oscillators.

In the automatic operation of the device the condenser I4 is set to the desired radio frequency and the volume control potentiometer 28 is set to the desired value. Thereafter motor 60 is started so as to vary the condenser I6 through the desired range and the sound waves are caused to affect the auditory nerve of the patient by.I connecting him to one of the telephone receivers and plug- Y ging the latter into one vof the jacks 38 or 40.

Thereafter the device continues to vary the sound waves as aforedescribed and illustrated in Fig. 5, until terminated.

By employing resistance couplings in all stages between the oscillators and the final output tube the heterodyne wave form which is produced originally by the oscillators is preserved, such wave form being substantially as shown in Fig. 2..

It will be noted that during the one half cycle the wave shape is almost rectangular while during the intervening half Acycle the wave form is sharply peaked, such a form having proved to be most particularly suited for the purpose in question. My present theory is that the effect is due to the relatively sudden impact of the sound followed by a relatively long sustained maximum pressure during substantially one half of each cycle of the sound wave as clearly illustrated in Fig. 2.

Fig. 3 shows Ath/elrelation between the dial setting for the condenser I6 and the frequency of the output energy. It will be noticed that there exists a substantially straight line relation between the dial setting and frequencies fromv1000 to '10,000 cycles, this being the fundamental frequencies which are most desired in the application of the apparatus. Inspection of Fig. 4 fur-- thermore indicates that thenutput of the apparatus within the range in which the relation between dial setting and frequency is linear remains substantially constant for all dial settings, that is, the output remains constant irrespective of the frequency, a characteristic which is highly desirable and important for the use of the appa- 'l ratus. V

What I claim as new and desire to secure by Letters Patent is: Y v l 1. An electronic generator of sound Waves comprising means for producing continuous trains of waves having a wave shape which is substantially rectangular during half cycles of one polarity and substantially triangular during the alternate half cycles, said means including two adjustable radio frequency oscillating circuits,.each including an electronic tube having a control grid and an anode, means to bias said grid so as to reduce discharge through saidy tube to substantially zero value during a substantial portion of a cycle and a relatively low impedance in series with said anode, and further means to superimpose the output of one circuit upon the output of the other tially rectangular during half cycles of one polarity and substantially triangular during the altervnate half cycles, said means including two yadjustable radio frequency oscillating circuitsA each including an electronic tube having a control grid and an anode, means to bias said gridA so as to reduce discharge through said tube to substantially zero value during a substantial portion of each cycle, a relatively low impedance in series with said anode, and means to vary the frequency of oscillation of at least one of said circuits, and further meansto superimpose the output `of one circuit upon the output of the other circuit.

3. An .electronic generator of sound waves comprising means for? producing continuous trains of waves having a wave shape which is substantially rectangular during half cycles of'one p'olarity and substantially triangular during the alternate half cycles, said means including two adjustable radio frequency oscillating circuits each including an electronic tube having a control grid and an anode, means to bias said grid so as to reduce discharge through said tube to subof each cycle, a'. relatively low impedance in series with said anode, and motor operated means adapted to cyclically vary the oscillating frequency ofA one of said oscillating circuits relative 'to that of the other of said oscillating circuits,

and vfurther means to superimpose the output of one circuit upon the output of the other circuit,

so as to produce a beat frequency equal to the desired sound frequency.

4. An electronic generator of sound waves, comprising means for producing continuous trains of waves having a wave shape which is substantially rectangular during half cycles of one polarity and substantially triangular during the includingathirdtuheandmemstoimpressthe 15 output of the fascinating .circuits upon samthird tube.

5. An electronic generator of sound waves of waves having a, wave shape which is substantially rectangular during half cycles of one polcomprising means for producing continuous trains 4 larity and substantially triangular during the aly ternate half cycles, said means including two radio frequency oscillating circuits, the frequency-- of at least one of which is adjustable and each including an electronic tube having a control grid and an anode, means to bias said grid so as to reduce discharge through said tube to substantially zero value during a substantial portion of a cycle and an external impedance in series with i said anode which is low in relation to the internal impedanceof said tube, an amplifier and sound output means including a third'tube and means to impress the output of the oscillating circuits upon said third tube.

6; An electronic generator of sound waves comprising means for producing continuous trains of Waves having a wave shape which is substantially rectangular during half cycles of one polarity and substantially triangular during the alternate half cycles, said means including two radio fre-A quency oscillating circuits, each 'including an electronic tube having a control grid and an anode, means to bias said grid so as to reduce discharge through said tube to substantially zero value during a substantial portionfof a cycle and an external impedance in series with said anode which is low in relation to the internal impedance of said tube, an amplifier and sound output means including a third tube, means Vto impress the output of said oscillating circuits upon said third tube and means to vary the oscillating fre-` quency of one of said oscillating circuits relative to that of the' other of said oscillating-circuits so as to produce a beat frequency equal to the I vdesired sound frequency.

'1. An electronic generator of sound waves comprising means for producing continuous trains of waves having a wave shape which is substantially rectangular during half cycles ,of one polarity and substantially triangular during the alternate half cycles, said means including two adjustable raidio frequency oscillating circuits, each includ ing an electronic tube having a control grid and an anode, means to bias said grid so as to reduce discharge through said tube to substantially z'ero value during a substantial portion of a cy- -of the output of said tube to substantially zero value during-.a substantial part of a cycle and further including an external plate impedance load which is low relative to the internal impedance of said tube, and an amplifying'tube receiving the output of said first mentioned tubes.

9. An audio frequency oscillator comprising two oscillating circuits, each of said circuits including a tube having a grld'and an anode, means adapted `to control said circuits. to oscillate at radio frequency including means to impress a high positive bias on said grids and to cause reduction of the output of said tube to substantially zero value during a substantial part of a cycleand further including an external plate impedance load which is low relative to the internal impedance of said tube, an amplifying tube receiving the'output of said first mentioned tubes.

and electromagnetic means to convert the electrical output of said third tube into sound waves. 10. An Aaudio frequency oscillator comprising two oscillating circuits, each of said circuits including a tube having a grid and an anode, means adapted to control said circuits to oscillate at radio frequencyv including means to impress a high positive bias on said grids and to cause reduction of the output of said tube to substantially zero value during a substantial part of a cycle and further including an external plate impedance load which is low relative to the internal impedance of 'said tube, means to vary the oscillating frequency of at least one of said circuits, and an amplifying tube receiving the output of said first mentioned tubes.

l1. An audio frequency oscillator comprising' two oscillating circuits, each of said circuits including a tube having a grid and an anode, means ,adapted to control said circuits to oscillate at radio frequency including means to impress a high positive bias on said grid and to cause reduction of the output of said tube to substantially zero value during a substantial part of a cycle and further including an external plate impedance load which is low relative to the internal impedance of said tube, means to vary the oscillating frequency of at least one of said circuits, an amplifying tube receiving the output of said first mentioned tubes, and electrochemical means to convert the electrical output of said third tube into sound waves.

12. An audio frequency oscillator comprising two oscillating circuits. each of said circuits including a tube having a grid and an anode, means adapted to control said circuit to oscillate at radio frequency including means to impress a high positive bias on said grid and to cause reduction of the output of said tube tosubstantially zero value during a substantial part of. a cycle further including an external plate iinpedance load which islow relative to the internal impedance of said tube, motor operated means adapted to cyclically vary the oscillating frequency of at` least one of said circuits to produce a heterodyne frequency within the audible range of sound, an amplifying tube receiving the output of said rst mentioned tubes, and electromechanical means to convert the electrical output vof said third tube into sound waves.

13. In the production of sound waves whose pitchvaries periodically between a given minimum and maximum, the steps of generating two superposed alternating voltages of frequencies above that of audible sound, periodically` varying the frequency of one of said voltages to produce with the other of said voltages a beat v,frequency which varies between said minimum and maximum, and the further step .of converting the elecv trical energy represented by said beat frequency 14. In the production of \sound waves whose pitch varies periodically between a given minimum and maximum. the periodic variations having superposed thereon a second series of periodic, variations of a different frequency, the

steps of generating two superposed alternating voltages of frequencies above that of audible sound, periodically varying the frequency of one of said voltages to produce with the other of said voltages a beat frequency which varies between said minimum and maximum, superpose upon said beat frequency another periodic variation of a different frequencywithin the audible range, and converting the electrical energy represented by said modied beat frequency into audible sound. 

